MicroGrinding News - Volume 1, Issue 1
DIAMONDS
MicroGrinding Systems has recently had an opportunity to do a test grind on industrial diamonds for a client. Imagine having a whole pallet - several hundred pounds - of diamonds sitting in your warehouse. The object was to grind the diamonds to an average particle fineness of five microns. The VKE mill did an outstanding job on grinding this hardest of materials using standard steel rods.
Actually, the harder the better for the VKE mill. Softer materials like talc tend to coat the rods or balls and do not grind as well in the vibratory mill as harder materials. A wet grind is usually better for soft materials. The VKE mill can be operated either way. Tube wear is negligible, but there is normal media wear.
VKE MILL IMPROVEMENTS
The quest for improvement never stops, and this is certainly true in the grinding mill business. The VibroKinetic Energy (VKE) mill represents the first major improvement in vibratory mill design since the Germans developed the Palla mill after World War II.
Although the principle is the same - vibrating the grinding vessel very hard and very fast - the VKE mill is the first and only mill to completely suspend the grinding chamber in a circle of heavy springs and put back into the mill action, thus saving a lot of energy.
Since the VKE mill was introduced several years ago, a number of further improvements have been incorporated into the original concept design in order to make the mill even better. A new and stronger frame was designed to better handle the enormous forces generated within the mill, and more and stronger springs were added for the same purpose and to provide smoother operation. A stronger motor mount was developed to strengthen the grinding chamber tube.
NEW LAB - SIZE UNIT IN THE WORKS
Due to popular demand, a small laboratory - size VKE mill will be produced. This new mill will be in production in early 1996 and will be available for sale or short term rental for those who wish to run tests in their own lab. The units will be complete with feeder and small dust collector to make up a self contained system.
The lab mill unit tube size will be approximately five inches inside diameter and twenty inches long. This unit will be helpful for initial test grinds or experimental work, plus be easily transportable to customer locations or trade shows for on-site demonstrations and test grinds. The VKE line will then consist of three basic models - the standard 2080 VKE mill (20 inch ID x 80 inches long); the 1040 Pilotmill (10 inches ID x 40 inches long); and the 520 Laboratory mill (5 inches ID x 10 inches long).
GRINDING VERMICULITE TO TIGHT SPECS
MicroGrinding Systems, at the request of a customer, has set up a custom grinding mill system at the Little Rock plant to grind a hard vermiculite ore to rather tight specifications. Three VKE mills are employed, along with supporting conveyors, screens, and dust collectors, to produce tonnage quantities of vermiculite per year, ground to a narrow size specification. Vermiculite is used in many different applications and we are not at liberty to divulge the ultimate use of this interesting material, but the application is an ongoing process and we expect to be producing this material for some time to come.
A certain percent of the feed ore winds up as fine material. Too fine for the intended application, and we are seeking a market for around two thousand pounds a day of this very fine, non-exfoliated vermiculite ore. Fine vermiculite finds use in certain ceramics and refractories, and as fillers in plastics and coatings. Also, due to the ion exchange effect of finely ground vermiculite, some work has been done in using the material to scavenge heavy metals from liquids containing heavy metal contaminants. The resulting residue is rich in the heavy metals and does not generate a bulky sludge, as does the more common flocculating agents used for this purpose. For samples of this fine vermiculite call or fax us here at MicroGrinding Systems. One known unusual application for fine vermiculite was tested several years ago to help wash out "dams" in rotary slagging kilns. It was found that the addition for an amount of vermiculite fines in the kiln feed reduced the viscosity of erosion of the dam, thus avoiding excess buildup in the kiln.
The VKE mills proved to be the most economical and practical choice for grinding this vermiculite ore and achieving optimum production of the desired type material. Three mills running continuously every day have proven reliable and trouble-free during the several months the custom milling setup has been in operation. Let us know if you have need for custom grinding of difficult material and we will do our best to be of assistance.
FINE GRINDING RELEASES ORE VALUES
As higher grades fo precious metals ores become more difficult to find, and as recovery processes are improved, more abundant lower value ores containing microscopic metal values are becoming more economically attractive to mine and process. The old timers would never have suspected the ores mined profitably today, like the Carlin trend ores where no gold is visible to the naked eye, would yield substantial amounts of precious metals.
The finely disseminated values, however, are often encapsulated in quartz to the point where it is necessary to crack the particles into tiny fragments in order to free the precious metal particles or expose them to leach extraction solutions. Thus is it necessary to grind the concentrates much finer than ever before, and this is where the VKE mill has shown to be most useful. Find grinding costs money, and milling costs can be a major part of the expense of extraction. The efficiency of the VKE mill can mean the difference between a marginal operation and a profitable mine. The optimum release size for many ores is at the minus 200 mesh range, but some require grinding even finer. A comparison of electrical energy grinding costs indicate the VKE mill as the lowest cost, with the Palla vibratory mill second at roughly twice the cost, and a conventional ball mill coming in third at three times the cost of milling the same ore using a VKE mill.
Basically we are talking about chemical reactions, in precious metals leach operations. And it stands to reason that the finer the ore, the faster and more efficient the reaction. The same is true in other chemical reactions as well, and the VKE mill is finding application in chemical ultrafine grinding in order to produce more reactive materials.
MicroGrinding News is published every now and then by the staff of MicroGrinding Systems for the enlightenment, amusement, and amazement of that rare group of rugged individuals who are involved with the special science of beating rocks and other hard stuff into little bitty pieces. Call or fax us at (501)-374-8402 for questions regarding your special applications, or news of interest to the industry. MicroGrinding Systems, Inc., 1823 East 17th Street, Little Rock, AR 72202 USA